Spectroscopic in solution

Note, however, that although the telluroketone [C6H4(CMe2)2CTe] is dimeric in the solid state, the monomer has been characterized spectroscopically in solution Mi-noura, M. Kawashima, T. Okazaki, R. J. Aon. Chem. Soc. 1993,115, 7019 Minoura, M. Kawashima, T. Okazaki, R. Tetrahedron Lett. 1997, 38, 2501. For a review of terminal chalcogenido complexes, see Kuchta, M. C. Parkin, G. Coord. Chem. Rev. 1998, 176, 323. 

The keto-enol tautomerism in 4-hydroxy- 1,5-naphthyridine (14) has been studied spectroscopically in solution and in the solid state.32 The keto form (15) is said to predominate in polar solvents and the enol form (14) in nonpolar solvents. 

Many other chromophores of the type CUN2O2 have been studied spectroscopically in solution, but little quantitative data have been obtained regarding the ligand field splitting. 

The hafnium complexes 9 and 16, respectively, with their preformed 1,3,5-triphosphinine ligands, are suitable substrates for the preparation of the nickel complex 24 [29]. In addition to the complexes with 7] -coordination, a platinum complex with fj -coordination is known. Complex 25, characterized spectroscopically in solution, undergoes hydrolysis with oxidation of the phosphorus atoms of the triphosphinine to afford the f] -platinum complex 26 possessing a hexahydrotriphosphinine ligand in the boat form as demonstrated by an X-ray crystallographic analysis [30]. 

For [R(Cl)GaAs(CH2SiMe3)2] (R = Me, Ph) the dimer-trimer equilibrium is detected spectroscopically in solution [261]. Cryoscopic and H and P NMR studies suggest that the degree of association of R2M-ER2 compounds in solution is controlled by thermodynamic factors such as solvation energies and entropic effects rather than kinetic factors [245, 262]. 

When ligands 7-R (R = Et, Ph, tBu, Scheme 5.5) were treated with [Rh(COD)Cl]2 in a 2 1 molar ratio, a single product with the stoichiometry RhCl(COD)(7-R) was obtained [76]. In contrast to the behaviour observed for the Ir system (vide infra), all three complexes exhibited a resonance at similar values, strongly indicating the same coordination mode for the three ligands with respect to Rh When the reaction was carried out in a 1 1 molar ratio, a P resonance at a slightly different chemical shift was obtained and attributed to complex [Rh(COD)(7-R)] [Rh(COD)Cl2] by analogy with the Ir system. These complexes were only characterized spectroscopically in solution. 

In solution, nanocrystals are ideal spectroscopic samples however many of dieir most important properties can only be realized when diey are assembled into more complex stmctures. One way of building complex stmctures is to rely on die inlierent tendency for monodisperse spheres to crystallize. Figure C2.17.3 shows die hexagonal close-... 

Until this time alkyl cations were considered only transient species. Their existence had been indirectly inferred from kinetic and stereochemical studies, but no reliable spectroscopic or other physical measurements of simple alkyl cations in solution or in the solid state were obtained. 

Addition of water to solutions of nitric acid in 90% sulphuric acid reduces rates of nitration. Between 90% and 85% sulphuric acid the decrease in rate parallels the accompanying fall in the concentration of nitronium ions. This is good evidence for the operation of the nitronium ion as the nitrating agent, both in solutions more acidic than 90% and in weakly diluted solutions in which nitronium ion is still spectroscopically detectable. 

Inorganic flocculants are analyzed by the usual methods for compounds of this type. Residual metal ions in the effluent are measured by spectroscopic techniques such as atomic absorption. Polymeric aluminum species formed in solution have been characterized by Al-nmr (64). 

A number of reaction products have been isolated from the (Tj -C H )2TiCl —N2—reductant system, where n = 1, 2, all of which assume an intense blue color in solution. Spectroscopic absorption occurs at a maximum, of ca 600 nm. The relationship among these products is unclear (185,186), but the labihty of the ring maybe an important complicating factor. When (Tj -C R 2TiCl2 [11136-36-0] R = CH3, is used, two distinct interconvertible... 

Two techniques for sorption-spectroscopic determination of ascorbic acid have been proposed. The first one is the recovery by silica modified with tetradecyl ammonium nitrate of blue form of molibdophosphoric HPA in the presence of vitamin C. And the second one is the interaction between the ascorbic acid in solution and immobilized on silica ion associate of molibdophosphoric acid with lucigenine. The detection limits of vitamin C are 0.07 and 2.6 mg respectively. The techniques were successfully applied to the determination of ascorbic acid in fmit juices. 

BBT solution on unmodified sorbents of different nature was studied. Silica gel Merck 60 (SG) was chosen for further investigations. BBT immobilization on SG was realized by adsoi ption from chloroform-hexane solution (1 10) in batch mode. The isotherm of BBT adsoi ption can be referred to H3-type. Interaction of Co(II), Cu(II), Cd(II), Ni(II), Zn(II) ions with immobilized BBT has been studied in batch mode as a function of pH of solution, time of phase contact and concentration of metals in solution. In the presence of sodium citrate absorbance (at X = 620 nm) of immobilized BBT grows with the increase of Cd(II) concentration in solution. No interference was observed from Zn(II), Pb(II), Cu(II), Ni(II), Co(II) and macrocomponents of natural waters. This was assumed as a basis of soi ption-spectroscopic and visual test determination of Cd(II). Heavy metals eluted from BBT-SG easily and quantitatively with a small volume of HNO -ethanol mixture. This became a basis of soi ption-atomic-absoi ption determination of the total concentration of heavy metals in natural objects. 

The solubility of AS2O3 in water, and the species present in solution, depend markedly on pH. In pure water at 25°C the solubility is 2.16 g per lOOg this diminishes in dilute HCl to a minimum of 1.56g per lOOg at about 3 m HCl and then increases, presumably due to the formation of chloro-complexes. In neutral or acid solutions the main species is probably pyramidal As(OH)3, arsenious acid , though this compound has never been isolated either from solution or otherwise (cf. carbonic acid, p. 310). The solubility is much greater in basic solutions and spectroscopic evidence points to... 

H 72.8, O 141.0 and I 295.2 kJ mol . Consistent with this the compound CsAu has many salt-like rather than alloy-like properties and, when fused, behaves much like other molten salts. Similarly when Au is dissolved in solutions of Cs, Rb or K in liquid ammonia, the spectroscopic and other properties are best interpreted in terms of the solvated Au ion (d °s ) analogous to a halide ion (s p ). 

Monosubstituted hydrazones of isatin can exist in at least three tautomeric forms 124-126. According to spectroscopic data, only hydrazone 124 is present in solution (81JOC2764). 

Unexpectedly strong intermolecular hydrogen bonding has been reported by IR spectroscopic studies for tetrahydro-4,7-phenanthroline-l,10-dione-3,8-dicarboxylic acids, which exist in the oxo-hydroxy form 165 in both solid state and in solution [78JCS(CC)369].Tlie conclusion was based on comparison of B-, C-, and D-type bands for 165 and their dimethyl esters (detection of hydrogen bonding) and on analysis of IR spectra in the 6 /xm region (pyridine- and pyridone-like bands). 

In an attempt to explain the peculiar photochemical behavior of 2,2,4,6-tetra-phenyldihydro-l,3,5-triazine, Maeda and coworkers carried out extensive studies on the annular tautomerism of this compound and its variously substituted derivatives both in solution and in the solid state. Thus, spectroscopic studies ( H NMR, IR, and UV) of 2,2,4,6-tetraphenyldihydro-l,3,5-triazine 105 (R = Ph) and some... 

Spectroscopic studies of ion-ion-solvent interaction in solutions containing oxyanions. D. W. 

The FT-IR spectroscopic measurements shown that in most cases the -COO or -0 groups formed a bridge between two Sn central atom, and polymerization occurred. The pqs approximations proved the formation of complexes with Oh, Tbp, and structures. H NMR measurements performed in DMSO solution have shown that the polymeric structure of the complexes does not persist in solution, and depolymerization occurs.. ... 

Amides are derivatives of carboxylic acids, so that their coordination behavior to boranes might be similar to that of their parent compounds. B-NMR spectroscopic studies have shown that compounds 31 and 32 are monomeric species in solution, while compounds 33 and 34 with the more Lewis acidic 9-borabicyclo[3.3.1]nonyl unit form aggregates that may be dimeric, oligomeric, or polymeric. The grade of association could not be determined by mass spectrometric analyses, because in all cases only the monomer is liberated into the gas phase [65]. 

Consequently, due to preferred cis-cis orientation a dimeric structure is observed for the indium complex and an unprecedented cis-trans arrangement in the thallium structure leads to a polymeric aggregate. Further N-NMR spectroscopic studies show that the aluminum and gallium complexes are stable contact ion pairs even in solution whereas the indium and thallium compounds are solvent-separated ion pairs in THE solution. 

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